The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Furore over coalition disunity claims

Senior Abbott government ministers have rejected claims of disunity and leadership turmoil after the federal budget.

Federal parliament descended into farce on Thursday when Labor used question time to seize on a report that Nationals ministers were duped into supporting a key budget measure.

The ABC said senior Liberals had deliberately leaked the idea of removing the $5.5 billion diesel rebate for miners and farmers in a bid to inflame the Nationals so they would support the reintroduction of fuel excise as the lesser of two evils.

The debate came as cabinet minister Malcolm Turnbull, a former Liberal leader, again fended off suggestions from conservative critics he was actively undermining Prime Minister Tony Abbott, who is overseas on a trade and security tour.

Raising the ABC report in parliament, Opposition Leader Bill Shorten asked whether there was "anyone in Australia that this prime minister has not lied to?".

"Why has this government spent all week undermining each other?" he said.

Acting Prime Minister Warren Truss dismissed the report's assertions as "simply wrong", saying the coalition was strong and based on an atmosphere of trust and reliance on one another.

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Any risk to fuel prices came from Labor's support for extending the carbon tax to transport fuels, he said.

In a lively rebuttal, Nationals deputy leader Barnaby Joyce referred to "rumours" about the NSW branch of the ALP, some of whose members had found themselves before the state's Independent Commission Against Corruption.

He had also heard deputy Labor leader Tanya Plibersek was after Mr Shorten's job.

"I heard someone from the NSW Right got convicted by the ICAC for corruption - hang on, that is the truth."

Mr Turnbull told parliament Mr Shorten was a "hollow man" and had a history of knocking off Labor leaders.

"They say they don't like (budget) cuts. He's been very good with a knife in the past."

Mr Turnbull had earlier tackled claims by conservative commentators he was being disloyal.

"We are a team. Tony and I are a team," he said, adding that commentators such as Andrew Bolt and radio host Alan Jones were the "bomb throwers".

"I will not stand by and let that falsehood be peddled," Mr Turnbull told the ABC on Thursday night.

"Because there is a risk that if you don't stand up to bullies and people who peddle these lies, that they will start to be accepted."